Lattice-bridge



l UNITED STATES PATENT GEFICE.

LUCIUS E. TRUESDELL, OF VARREN, MASSACHUSETTS.

LATTICE-BRID GE.

Specification of Letters Patent No. 15,048, dated June 3, 1856.

T0 all whom it may concern Be it known that I, LUoiUs E. TRUESDELL, of IVarren, in the county of Worcester and State of Massachusetts, have invented a new and useful Improvement in Veight-Distributing Bridges, of which the following is a full, clear, and exact description, reference being had to the accompanying drawing of the same, in which- Figure l represents a side elevation of a bridge for ordinary purposes embracing my improvements; Fig. 2, a similar view of one when extraordinary strength is required as in cases of rail road bridges, &c., and F ig. 3, an end view of the same.

My improvements are specially adapted and intended to be applied to bridges constructed of wood, or of iron, and relate more particularly to a new mode of bracing that class of the same called lattic frame bridges;

' whereby any weight, or strain, thrown upon any part of it is distributed equally over the whole in all directions, a point of paramount importance, and which has not hitherto been accomplished by any of the known modes of bracing, which enables me to obtain a greater strength from a much less amount of material than has hitherto been necessary for the construct-ion of bridges of a given strength, in this way relieving the piers and abutments of much of the enormous strain and crushing weight to which they are at present subjected. This in one class arises from the peculiar mode of bracing pursued, wherein the braces are secured diagonally as in the St. Andrews cross thus throwing the strain endwise in a horizontal line with the length of the bridge, causing the string and horizontal beams on the application of pressure to approach each other and finally to collapse and break down. In others wherein the brace used is secured in a vertical position and in the line of pressure, it is caused to support the whole weight and strain without receiving any assistance from the united strength of the bridge; whereas by my improved mode wherein both the vertical and horizontal braces are combined, the strain is distributed equally over the whole bridge both in a vertical and horizontal direction. In the former cases these defects have been attempted to be removed by passing diagonal braces and struts across the bridge, as well as by additional strings or binding beams in a horizontal direction, as also by trusses and a variety of other devices, but even then these defects are only partially removed, and that at such an expense as to vastly increase the weight of the bridge, and its cost of construction, as well as of its piers and abutments.

In the accompanying drawings A, A, represent rafter timbers intersecting each other at an angle of about 90o and a t equal distances apart forming a continual lattice frame so that the spaces created by their intersection form squares having one of their diagonal lines perpendicular to and the other parallel or nearly so with the string timbers (B,) of which there are two on either side, between and to which the lower ends of the rafters 'are firmly secured by bolts These rafters rise from the beam (B,) at an angle of about 45, and are halved into, and secured to each other, by bolts or pins (a) at the points of their intersect-ion. Between the angles of the squares thus formed, are secured horizontal braces (0,) parallel with the string timbers (BQ these being intersected at right angles by vertical braces (d) passing between the upper and lower angles of the same squares, both being halved into each other and firmly bolted together, and otherwise secured to the rafter timbers in any suitable manner. These braces serve to distribute the weight or pressure communicated to any part of the bridge over the whole, and thus relieve those parts immediately in the plane of pressure from undue strain. Upon the string beam B, is secured an under flooring (F;) or instead of being supported upon the string beams directly it may, if thought advisable, be secured upon bed plates secured to the horizontal braces (o). To prevent any independent lateral play of the sides of the bridge, cross ties (Gr,) may be passed across and firmly bolted to their upper sides in order to connect them rigidly together, so that in the event of a swinging lateral motion being communicated to the bridge by the passage of a train of cars, wagons, &c., over it, both sides shall vibrate equally, and thus prevent any undue strain upon the other parts of the bridge, such as would otherwise occur were both ina measure independent of each other save from that necessarily given by their lower connections.

In F ig. 3, are represented cross ties resting and secured upon the horizontal braces (C) having rails (I) secured to and supported upon their upper sides, for the A passage of a train of cars.

In other bridges it has usually been found absolutely essential to have upper ties connectng the rafters together to obtain the requsite strength to support a heavy moving Weight, but With my improved mode of bracing, a bridge is as strong Without as with it, and saves Weight and consequent strain. The only object of using such a tie beam or sill With mine would be to roof in the bridge to protect it from the Weather.

What I claim as new and desire to secure by Letters Patent is)- The braces (C, D,) in combination With the rafters (A,) When arranged in the manner substantially as, and for the purposes described. l

In testimony whereof I hereunto set my hand in presence of tvvo subscribing Witnesses.

L. E. TRUESDELL.

Attest MARGELLUS SToors, P. HANNAY. 

